Catalytic automotive exhaust converter



Aug. 6, 1963 P. R. ASHLEY ETAL 3,100,140

CATALYTIC AUTOMOTIVE EXHAUST CONVERTER Filed May 31, 1960 INVEI'Z: RSPAU .ASHL

DAV .LAING ATTORNE S United States Patent 3,100,140 CATALYTIC AUTOMOTIVEEXHAUST CONVERTER Paul R. Ashley, Livonia, and David D. Laing, Detroit,M ch assignors to Calumet & Hecla, Inc., Allen Park, Mich., acorporation of Michigan Filed May 31, 1960, Ser. No. 32,678 6 Claims.(Cl. 23-288) This invention relates to a catalytic automotive exhaustconverter and method of making the same.

One object of this invention is to provide a catalytic automotiveexhaust converter for use in the exhaust line of an internal combustionengine to remove unburned hydrocarbons and other objectionablecomponents from the exhaust gases, which converter is designed to behighly eflicient in the performance of its intended function.

Another object of the invention is to provide a catalytic automotiveexhaust converter which is less expensive to manufacture than prior artconverters of this type.

A further object of the invention is to provide an exhaust convertercomprising a casingv having a chamber therein, a plurality ofsuperimposed sheet layers in the chamber which are corrugated in thesame direction and the peaks of which engage one another to definechannels, and catalytic material in the channels to accelerate theoxidation of the unburned hydrocarbons passing through the channels.

Still another object of the invention is to provide an exhaust converteras described above in which the peaks of the corrugations of alternatesheets are formed with generally V-shaped longitudinal recessesreceiving the peaks of the corrugations of the remaining sheets toprovide a mechanical interlock.

Another object of the invention is to provide an exhaust converter asdescribed above in which the body of the casing is formed from a singlecorrugated sheet of material spirally rolled upon itself, the peaks ofcertain of the corrugations being recessed so that the corrugations ofoverlying layers form a mechanical interlock.

Another object of the invention is to provide a method of making theexhaust converter described above.

Other objects and features of the invention will become apparent as thedescription proceeds, especially when taken in conjunction with theaccompanying drawings, wherein:

FIGURE 1 is a perspective view of a catalytic automotiveexhaustconverter constructed according to our invention.

FIGURE 2 is an enlarged fragmentary perspective view of one end of theconverter with parts removed to illustrate the interior construction.

FIGURE 3 is an end view of the structure shown in FIGURE 2.

FIGURE 4 is a sectional view taken on the line 44 of FIGURE 3.

FIGURE 5 is an enlargement of a portion of FIG- URE'3.

FIGURE 6 is a perspective view showing an intermediate step in theconstruction of the converter.

Referring now more particularly to the drawings, the exhaust converterthere shown comprises the elongated casing 10 which has an outer tubularwall 12 and an inner tubular wall 14 which cooperate to define anelongated annular chamber 16 between the walls of the casing.

The inner and outer Walls of the casing, as well as the interior sheetlayers thereof, described more fully hereinafter, are formed from asingle elongated sheet 20 which may be aluminized steel, for example, orany other suitable high heat conductivity material. The sheet is notchedalong both of its longitudinal edges to provide the intermediate section22 of uniform width, the ends 24 and 26 of the sheet being relativelybroad and of the same width. The intermediate section 22 of the sheet istransversely corrugated throughout its length, as shown. The end 26 hasa transverse fold 27 near the corrugated intermediate section and atransverse flange 29 along its edge.

In order to build the converter, the broad end portion 24 of the sheet20 is folded upon itself to provide the elliptical inner wall 14 andseam welded at the joint 28. The seam weld extends along the innertraverse edge of the broad portion 24, joining the already formed innerwall 14 to the intermediate section 22 in a continuous weld at the pointwhere they diverge. The inner wall 14 thus forms an air-tight tube.Thereafter, the corrugated intermediate section of the sheet is spirallywrapped about the inner wall 14 of the casing to provide a plurality ofsheet layers, as shown in FIGURE 3. All of the corrugations aregenerally V-shaped. The corrugations of the first layer or spiral areformed with generally V-shaped recesses 30 which extend from end to endof the corrugations and are formed to receive the peaks of certaincorrugations of the outer layer or spiral. Hence the corrugations of onelayer are mechanically interlocked with the corrugations of the otherlayer. In the particular design shown, it was found desirable to' locatefour peaks 31 in positions other than on the V-shaped recesses 30.

In the present embodiment, only two layers of corrugations are provided.However, it will be appreciated that additional layers or spirals of thecorrugated intermediate section of the casing may be provided, in whichevent the corrugations of alternate layers will be formed with theV-shaped recesses in their peaks to receive the peaks of thecorrugations of the adjacent layers. Channels 34 are defined by thecorrugations.

The sheet 20 is completely wrapped upon itself so that the broad endsection 26 provides an outer Wrap and defines the outer wall 12 of-thecasing. When the final router wrap is made, the flange 29 is hooked overthe told 27 and the two are flattened down substantially parallel to thesurface of the outer wall 12 of the converter. This is one preferredmeans for securing the outer wrap. It will be understood that othermeans may be employed. For example, the end of the outer wrap may simplybe seam welded. Clearly other suitable means for fastening the outerwrap may be provided. It will be appreciated that the length of thecasing is equal to the width of the end portions 24 and 26 and that thechannels 34 defined between the corrugations of adjacent sheet layersare shorter than the casing. The purpose of this is to provide thechambers 36 and 38 at opposite ends of the casing, more fully describedhereinafter.

Annular screens 42 are shaped to fit closely within the outer wall 12and to fit closely about the inner wall '14, and are inserted within theends of the casing. Any suitable means may be employed to securelyfasten the screens in position against the ends of the channels so thatthe catalyst cannot escape and so that channeling cannot occur. In thepresent instance, the screens are shown by way of example as havingretainer rings 43 spot welded to the casing. First, one of the screensis installed in position and the casing is placed on end and thengranulated catalytic material is poured into the channels 34 until theyare filled. Then the other screen is installed. The screen apertures aresomewhat smaller than the grains of catalyst to contain them withoutinterfering with the flow of exhaust gases through the channels.

The annular end closure members 44 are identical. They are formed withinner annular flanges 46 having a close fit about the inner wall 14 ofthe casing, and outer annular flanges 48 having a close fit within theouter wall 12 of the casing. Any suitable means may be provided tosecurely fasten the end closure members in positi'on at the endsof thecasing so that the space between the end closure members is relativelyleak-proof. In the present instance, and by way of example, the flangesare shown as welded to the casing, although it will be obvious thatother equally satisfactory fastening means may be employed. For example,instead of welding, the end members 44 may be rolled, crimped, orfastened in any other way to form an air tight seal around the innerwall 14 and the outer wall 12. One end member is formed with an exhaustinlet 50 and the other with an exhaust outlet 52. These inlets andoutlets may also be secured to the end menrbers by rolling, welding orany suitable means which provides an airtight seal. The chambers 36 and38 are defined between the screens and end members and are in directcommunication with the catalyst channels 3 4. The inlet 50' and outlet52 are at opposite sides of the center tube 14 to assure a betterdistribution of gases inside the converter.

No catalytic converter based on the oxidation of hydrocarbons can beeffective unless there is sufiicient oxygen introduced to complete thecombustion of the unburned hydrocarbons. Any other suitable airinspiration devices may be used to provide the necessary secondary air.The secondary air may, for example, be introduced by devices such as aventuri, a flat-plate orifice or a pump. The particular means forintroducing the secondary air forms no part of this invention andtherefore it should be understood that the converter may be used inconjunction with any suitable means for introducing secondary air.

The catalyst may be any suitable material designed to promote oxidationof the unburned hydrocarbons in the exhaust gases passing through theconverter. Vanadium pento-xide (V has been found to be a very effectivecatalyst for this purpose. as those of chromium, manganese, copper,nickel, iron and molybdenum might provide suitable catalysts. Since allcatalysts act only on their surface, they are usually coated on agranulated carrier. The dimensions of the granulated catalytic materialare not critical but they should not be so small as to pass through theretaining screen or to pack in a solid mass.

The sheet 20 is formed of a high heat conductivity material to rapidlydissipate the heat generatedin the. converter. The channels break up anduniformly distribute the catalytic bed so that it is kept at a more orless uniform temperature, thereby avoiding the for mation of hot spots.

The corrugations engage each other and engage the inner and outer wallsof the casing, but they may yield, or move, relative to one another toavoid damage due to mechanical and thermal shock. In this connection thepeaks of the corrugations which engage each other as well as the innerand outer walls 12 and 14 are, at least throughout a major part of thelength of such engagement, not fixedly secured in position. In some.in-. stances the entire length of engagement of the peaks of thecorrugations are free of any fastening means. However, in otherinstances it is desirable to weld or otherwise fasten the peaks of thecorrugations at the ends of the channels so that the size of theconverter can be closely controlled. Too much movement can ac-. tuallybe a detriment since it can grind the catalyst and allow it to move fromone channel to another. Therefore it is desirable to provide a smallamount of flexibility to avoid crushing the catalyst due to mechanicaland thermal shock and movements but the flexibility should be so limitedthat the catalyst will not 'be actually ground up in the process and thedimensions of the entire converter can be properly controlled duringmanufacture.

The channels have the further function of muffling noise by breaking upthe stream of gas. Basically, this is a process of dividing the gasstream up into a number of Other oxides such 4 small channels so that asthe sound waves pass out of the end of the converter they interfere witheach other to partially cancel the noise of the engine explosions.

The inner wall 14 of the casing defines a. through passage for air tofacilitate cooling olf the converter. In some instances it may bedesirable to provide an integral corrugated extension 56 of the broadend portion 24 which will bedisposed within the tubular wall 14 incontact therewith to serve as a reinforcement and as an additionalsurface for the dissipation of heat.

In designing and constructing a converter of this type, the first stepis to secure the following information:

1) The required catalyst section volume based on the amount of catalystneeded.

(2) The catalyst density.

(3) The physical dimensions of the place where the converter is to belocated.

(4) The size of the inlet and outlet pipes if predetermined by the enduse.

Using the above information, it is possible to determine the height,width, and length of the converter.

The following points must be considered when designing for automobileuse.

1) Heat transfer: Design for maximum allowable outside surface includingthe center cooling tube.

(2) Pressure drop across converter:

(a) Design for shortest catalyst bed length.

(b) Design to eliminate sharp turns in gas flow; for example, keepplenum chambers as large as practical.

(3) Mechanical strength: Design for curved surfaces.

After the outside and center tube dimensions have been determined, thecorrugated cross section is next considered. In deciding the insideconfiguration, all factors which affect channel size must be considered.

(1) The type of catalyst used must be considered. A soft, irregularshaped, rough surfaced, easily broken up catalyst requires smallerchannels than a hard, smooth surfaced, pelleted type.

(2) The amount of metal, and consequently the tinished weight of theconverter, depends on the size of the corrugations.

(3) Among other things, the attenuation qualities depend on the size ofthe channels.

4) The mechanical strength depends on the thickness of the material andthe number of channels. The smaller the channels the closer together thepeaks will be around the center tube and the outer casing. The number oflayers will be decided by the channel size desired. The first wrapautomatically decides the number of peaks in the second and anysucceeding layers. There must be one peak in the first layer for eachpeak desired in the second, third, or whatever layer is the final layerin direct contact with the outer casing. A rule of thumb could be statedthat the average channel area is from 2.5% to 5% of the total crosssectional area channel of the casing.

After the desired channel size has been approximated, the outer casingand the center cooling tube are laid out, in relation to each other, onpaper. When this layout is made, the distance on the flat plane from theouter casing to the center tube is divided in half and a line is scribedparallel to the flat surfaces at this point. The perimeter of thecooling tube is divided into the desired number of corrugations. Thedistance between any two of these points now becomes the base of ageneral triangle. A point on the outer casing is located for each pointon the cooling tube. This can be done by projection. On the circularends of the casing, it is often desirable to change the location ofthese points to gain meo'hanical strength or to equalize the size of thechannels. In this particular design, we found it necessary to locatefour peaks on the outer wrap. in positions other than on V-shapedrecesses of the first layer. After these points have been located, theytoo form the base of a general triangle which is inverted from the firsttriangle.

The next step is to locate a point midway between these sets of pointson the previously scribed line. This point, when connected to the twopoints on the outer casing, forms a triangle which becomes the outerlayer. The next step is to determine the desired depth of the interlock.After the depth has been decided, the designer should measure up on thealready form-ed outer triangle and locate the two points. These points,when connected to the points on the center cooling tube, form the inneror first channel. When :a pair of adjacent inner and outer channelsconnect in the interlock, they form between them a diamond shapedchannel.

After the size and shape of the corrugations have been determined, thenext step is to lay out the configuration using one continuous linerepresenting the single sheet construction. When preparing this, again,some important considerations must be noted:

(1) Weld locations should be readily accessible.

(2) Doubling the sheet should be avoided when it must fit into aninterlock or at any point where it might, when heated, open up andpermit direct channeling of the exhaust gases.

Only one step remains before construction of the casing can begin. Thisstep is to translate the design to a dimensioned drawing. This can bedone in any manner desired.

The drawings and the foregoing specification constitute a description ofthe improved catalytic automotive exhaust converter and method of makingthe same in such full, clear, concise and exact terms as to enable anyperson skilled in the art to practice the invention, the scope of whichis indicated by the appended claims.

What we claim as our invention is:

1. A catalytic exhaust gas converter comprising a casing having achamber therein extending longitudinally a substantial distance in adirection from an inlet end to an outlet end, a plurality ofsuperimposed heat conductive sheet layers in said chamber, adjacentlayers being corrugated to provide peaked portions which extendlongitudinally in the direction of and parallel to said chamber, withthe depth of said corrugations being transverse of said direction, saidcorrugated layers engaging one another to define laterally enclosedrectilinear channels open at opposite ends thereof, each channel beingof substantially uniform cross sectional area along the length thereof,granular catalytic material in said channels substantially filling thesame as subdivided masses of said material, and foraminated members atsaid opposite ends of said channels confining said catalytic materialtherein, said casing having inlet and outlet ports adjacent said inletand outlet ends which communicate respectively through said foraminatedmembers with said opposite ends of said channels for the passage ofexhaust gases through said catalytic material in the channels, saidchannels being individually in heat conductive and physically supportingrelation to the respective subdivided masses of the material in therespective channels.

2. A catalytic exhaust gas converter comprising a casing having achamber therein extending longitudinally a substantial distance in adirection from an inlet end to an outlet end, a plurality ofsuperimposed heat-conductive sheet layers in said chamber, adjacentlayers being corrugated to provide peaked portions which extendlongitudinally in the direction of and parallel to said chamber, withthe depth of said corrugations being transverse of said direction, asubstantial number of the peaked portions of the corrugations of onelayer engaging those of the corrugations of an adjacent layer to definelaterally enclosed rectilinear channels open at opposite ends thereof,each channel being of substantially uniform cross sec tional area alongthe length thereof, granular catalytic material in said channelssubstantially filling the same as subdivided masses of said material,and foraminated members at said opposite ends of said channels confiningsaid catalytic material therein, said casing having inlet and outletports adjacent said inlet and outlet ends which communicate respectivelythrough said foraminated members with said opposite ends of saidchannels for the passage of exhaust gases through said catalyticmaterial in the channels, said channels being individually in heatconductive and physically supporting relation to the respectivesubdivided masses of the material in the respective channels.

3. An exhaust gas converter in accordance with claim 1, in which saidcasing and channel-defining layers are integral parts of a single sheetof heat conductive material spirally wrapped upon itself to constitutesaid chamber and passages.

4. An exhaust gas converter in accordance with claim 2, in which saidcasing and channel-defining layers are integral parts of a single sheetof heat conductive material spirally wrapped upon itself to constitutesaid chamber and passages.

5. An exhaust gas converter in accordance with claim in which saidengaged peaked portions of adjacent layers have mating formations at thezone of engagement thereof to provide a mechanical interlock of saidportions.

6. An exhaust gas converter in accordance with claim 4, in which saidengaged peaked portions of adjacent layers have mating formations at thezone of engagement thereof to provide a mechanical interlock of saidportions.

References Cited in the file of this patent UNITED STATES PATENTS1,113,151 Chisholm Oct. 6 ,1914 2,361,691 Jendrassik Oct. 31, 19442,526,657 Guyer Oct. 24, 1950 2,576,213 Chausson Nov. 27, 1951 2,834,657Houdry May 13, 1958 2,853,367 Karol et al Sept. 23, 1958 FOREIGN PATENTS1,332 Great Britain Nov. 6, 1913 1913 137,556 Switzerland Mar. 17, 1930

1. A CATALYTIC EXHAUST GAS CONVERTER COMPRISING A CASING HAVING ACHAMBER THEREIN EXTENDING LONGITUDINALLY A SUBSTANTIAL DISTANCE IN ADIRECTION FROM AN INLET END TO AN